Spinal device including lateral approach

ABSTRACT

Embodiments of the invention include devices and methods for implanting a vertebral body spacer. A lateral surgical approach is contemplated with some disclosed procedures. Instruments of some embodiments are insertable into a disc space to achieve distraction, to determine a desired disc space height, and to select a corresponding implant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to a U.S. patent application entitled“SPINAL SYSTEM AND METHOD INCLUDING LATERAL APPROACH,” filed on the sameday as the subject application, and which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to the field of spinal implants,and more particularly relates to vertebral body spacers and methods ofimplanting vertebral body spacers.

BACKGROUND

Vertebral body spacers are used in response to degenerative disc diseaseor other spinal conditions to maintain a space between adjacent spinalvertebrae. Typically, the goal of an associated surgical procedure isfor the adjacent vertebrae to grow or “fuse” together. A vertebral bodyspacer is usually made of a biocompatible synthetic material orallograft bone.

Vertebral body spacers have been implanted from anterior,transforaminal, oblique, posterior, and other surgical approaches for anumber of years. A lateral surgical approach has also been accomplished.However, the prior implants, instruments, and methods associated with alateral approach are not optimal.

Existing implants used with a lateral approach may fail to conform tothe natural curvatures of vertebral endplates or to the natural anteriorcurves of the anterior portion of the vertebral body. Instruments andlateral implants are not necessarily suited to efficiently distract thedisc space without damaging the adjacent endplates. The shapes ofinstruments and lateral implants are not particularly coordinated toreduce disruption to the surrounding tissues. Current methods mayrequire significant cutting and manipulation of bone and other tissue.

The description herein of certain disadvantages and problems associatedwith known devices, apparatus, and methods is not intended to limit thescope of the invention to the exclusion of those known devices,apparatus, and methods. Embodiments of the invention may include some orall of the known devices, apparatus, and methods without suffering fromthe disadvantages and problems described herein.

Methods and devices for performing surgery are disclosed in U.S. Pat.No. 5,792,044, “Devices and Methods for Percutaneous Surgery,” filedMar. 22, 1996; U.S. patent application Ser. No. 10/274,856, “Systems andTechniques for Restoring and Maintaining Intervertebral Anatomy,” filedOct. 21, 2002; U.S. patent application Ser. No. 10/766,167, “Systems andTechniques for Restoring and Maintaining Intervertebral Anatomy,” filedJan. 28, 2004; and U.S. patent application Ser. No. 10/792,358,“Instruments and Methods for Minimally Invasive Tissue Retraction andSurgery,” filed Mar. 3, 2004, all of which are incorporated by referenceherein. Any of the relevant implants, instruments, methods, or surgicalapproaches described in the incorporated references that are adaptablefor use with components of the present invention and are within thescope of the invention described and claimed herein.

SUMMARY

One embodiment of the invention is an implant with an elongated bodypositionable in a spinal disc space. The embodiment has a convexlycurved upper surface orientable toward an endplate of an upper vertebra,a convexly curved lower surface orientable toward an endplate of a lowervertebra, a leading end portion, and an opposite trailing end portion.An at least partially convexly curved anterior sidewall extends betweenthe leading end portion and the trailing end portion, and a posteriorsidewall extends between the leading end portion and the trailing endportion. The body includes a height between the upper and lower surfacescorresponding to a desired disc space height between the upper vertebraendplate and the lower vertebra endplate. The leading end portion isstructured for insertion into the disc space in an at least partiallycollapsed condition and the height is sized to restore the collapseddisc space to the desired disc space height as the body is inserted inthe collapsed disc space.

An embodiment of the invention is an implant with an elongated bodypositionable in a spinal disc space. The embodiment has an upper surfaceorientable toward an endplate of an upper vertebra, a lower surfaceorientable toward an endplate of a lower vertebra, a leading endportion, and an opposite trailing end portion. An at least partiallyconvexly curved anterior sidewall extends between the leading endportion and the trailing end portion, and a posterior sidewall extendsbetween the leading end portion and the trailing end portion, theposterior sidewall having an average height less than the average heightof the anterior sidewall. At least one of the upper surface and thelower surface are curved such that the height of the implant near itscenter is greater than the height of the implant at its leading end. Theheight of the implant near its center is between about 7 mm and 19 mm.The height of the implant at its leading end is at least about 3 mm lessthan the height of the implant near its center.

Another embodiment of the invention is an implant with an elongated bodypositionable in a spinal disc space. The embodiment has a convexlycurved upper surface, a convexly curved lower surface, a leading endportion defined by a convexly curved surface that extends between theupper surface and the lower surface, and a trailing end portion definedby a substantially planar surface that extends between the upper surfaceand the lower surface. An anterior sidewall is defined by a maximallyanterior portion, a first curved portion extending between the leadingend portion and the maximally anterior portion, and a second curvedportion extending between the trailing end portion and the maximallyanterior portion. A posterior sidewall extends between the leading endportion and the trailing end portion. The height of the implant near itscenter is between about 8 mm and 14 mm. The height of the implant at itsleading end is at least about 3 mm less than the height of the implantnear its center.

An additional embodiment of the invention includes an implant with anelongated body positionable in a spinal disc space. The embodiment hasan upper surface means orientable toward an endplate of an uppervertebra for substantially cooperatively fitting with the uppervertebra, a lower surface means orientable toward an endplate of a lowervertebra for substantially cooperatively fitting with the lowervertebra, and a leading end means for promoting insertion of the implantbetween the upper vertebra and the lower vertebra, and an oppositetrailing end portion. The embodiment also has an at least partiallyconvexly curved anterior sidewall means for enabling anterior placementof a portion of the implant between the cortical rim of the uppervertebra and the cortical rim of the lower vertebra. A posteriorsidewall extends between the leading end means and the trailing endportion. The height of the implant near its center is between about 7 mmand 19 mm. The height of the implant at its leading end is at leastabout 3 mm less than the height of the implant near its center.

Yet another embodiment of the invention is a system for placing animplant between an endplate of an upper vertebra and an endplate of alower vertebra. The embodiment includes a trial instrument set with atleast two instruments of different sizes. Each trial instrument of thetrial instrument set has an upper surface orientable toward the uppervertebra, a lower surface orientable toward the lower vertebra, and aleading end portion with segments that diverge from the leading end tomeet the upper surface and the lower surface respectively. Theembodiment also includes an implant with an elongated body positionablein a spinal disc space. The implant has an upper surface orientabletoward the upper vertebra, a lower surface orientable toward the lowervertebra, a leading end portion and an opposite trailing end portion, anat least partially convexly curved anterior sidewall extending betweenthe leading end portion and the trailing end portion, and a posteriorsidewall extending between the leading end portion and the trailing endportion. At least one of the upper surface and the lower surface arecurved such that the height of the implant near its center is greaterthan the height of the implant at its leading end, and the height of theimplant near its center is between about 7 mm and 19 mm. The height ofthe implant at its leading end is at least about 3 mm less than theheight of the implant near its center.

Still another embodiment of the invention is a method of surgicallyplacing an implant between vertebral bodies from a generally lateralsurgical approach. The embodiment includes positioning a patient suchthat a coronal, operative side of the patient is accessible, making anincision in the operative side of the patient between the ribcage andthe iliac crest of the patient, locating an initial insertion dilatorbetween the vertebral bodies, dilating tissue with a first concentricdilator that fits over the initial insertion dilator to further open theincision, removing vertebral disc material to create an opening for theimplant between the vertebral bodies, inserting a trial instrumentbetween the vertebral bodies, and inserting between the vertebral bodiesan implant. The implant has an upper surface orientable toward the uppervertebra, a lower surface orientable toward the lower vertebra, aleading end portion and an opposite trailing end portion, an at leastpartially convexly curved anterior sidewall extending between theleading end portion and the trailing end portion, and a posteriorsidewall extending between the leading end portion and the trailing endportion. At least one of the upper surface and the lower surface arecurved such that the height of the implant near its center is greaterthan the height of the implant at its leading end. The height of theimplant near its center is between about 7 mm and 19 mm. The height ofthe implant at its leading end is at least about 3 mm less than theheight of the implant near its center.

Another embodiment of the invention is a method of surgically placing animplant between vertebral bodies from a generally lateral surgicalapproach. The embodiment includes positioning a patient such that acoronal, operative side of the patient is accessible, making an incisionin the operative side of the patient between the ribcage and the iliaccrest of the patient, locating an initial insertion dilator between thevertebral bodies, dilating tissue with a first concentric dilator thatfits over the initial insertion dilator to further open the incision,removing vertebral disc material to create an opening for the implantbetween the vertebral bodies, inserting a trial instrument between thevertebral bodies, and inserting between the vertebral bodies an implant.The implant has a convexly curved upper surface orientable toward anendplate of an upper vertebra, a convexly curved lower surfaceorientable toward an endplate of a lower vertebra, a leading end portionand an opposite trailing end portion, an at least partially convexlycurved anterior sidewall extending between the leading end portion andthe trailing end portion, and a posterior sidewall extending between theleading end portion and the trailing end portion. The body includes aheight between the upper and lower surfaces corresponding to a desireddisc space height between the upper vertebra endplate and the lowervertebra endplate. The leading end portion is structured for insertioninto the disc space in an at least partially collapsed condition and theheight is sized to restore the collapsed disc space to the desired discspace height as the body is inserted in the collapsed disc space.

An embodiment of the invention is a method of surgically placing animplant between vertebral bodies from a generally lateral surgicalapproach. The embodiment includes making an incision in an operativeside of a patient between the ribcage and the iliac crest of thepatient, inserting a trial instrument between the vertebral bodies, andinserting between the vertebral bodies an implant with an elongatedbody. The implant has an upper surface orientable toward an endplate ofan upper vertebra, a lower surface orientable toward an endplate of alower vertebra, a leading end portion and an opposite trailing endportion, an anterior sidewall defined by a maximally anterior portion, afirst curved portion extending between the leading end portion and themaximally anterior portion, and a second curved portion extendingbetween the trailing end portion and the maximally anterior portion, anda posterior sidewall extending between the leading end portion and thetrailing end portion. The act of inserting the implant includes placingthe implant anteriorly between the vertebral bodies such that the firstcurved portion and the second curved portion of the anterior sidewallare substantially located between a cortical rim of the upper vertebraand a cortical rim of the lower vertebra.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an implant of an embodiment of theinvention.

FIG. 2 is another perspective view of the implant of FIG. 1.

FIG. 3 is an end elevation view of the implant of FIG. 1.

FIG. 4 is an end elevation view of the implant of FIG. 1.

FIG. 5 is an end elevation view of an implant of another embodiment ofthe invention.

FIG. 6 is an elevation view of still another implant of an embodiment ofthe invention.

FIG. 7 is a cross-sectional view of the implant of FIG. 6.

FIG. 8 is a perspective view of a coupling member of an embodiment ofthe invention.

FIG. 9 is a perspective view of a distal end of the coupling member ofFIG. 8.

FIG. 10 is a perspective view of a coupling member of an embodiment ofthe invention attached to an implant.

FIG. 11 is a perspective view of the distal end of a coupling member ofanother embodiment of the invention.

FIG. 12 is a perspective view of an implant of another embodiment of theinvention.

FIG. 13 is a perspective view of a set of instruments of an embodimentof the invention.

FIGS. 14 a-f are partial cross-section and side elevation views ofembodiments of the invention applied to a spinal column.

FIG. 15 is a perspective view of a retractor in an insertionconfiguration.

FIG. 16 is a plan view of the retractor of FIG. 15.

FIG. 17 is a plan view of the retractor of FIG. 15 with a separationinstrument engaged.

FIG. 18 is a perspective view of the assembly of FIG. 17.

FIG. 19 is another perspective view of the assembly of FIG. 17 with theretractor portions separated.

FIG. 20 is a plan view of the assembly of FIG. 19.

FIG. 21 is a perspective view of the assembly of FIG. 19 with lever armsmoved to a pivoting position.

FIG. 22 is a sectional view of a portion of the separation instrumentthrough line 22-22 of FIG. 21 showing a lever arm locking assembly whenthe retractor portion engaged thereto is in a non-pivoted position.

FIG. 23 is perspective view of the separation instrument of FIG. 17detached from the retractor.

FIG. 24 is an elevation view of a portion of the separation instrumentof FIG. 17.

FIG. 25 is a perspective view of the assembly showing the retractorportions pivoted.

FIG. 26 is a sectional view through line 26-26 of FIG. 25 of a portionof the separation instrument showing the lever arm locking assembly whenthe retractor portion engaged thereto is in a non-pivoted position.

FIG. 27 is a perspective view of the assembly of FIG. 19 showing theretractor portions pivoted and a first intermediate retractor assemblyengaged to the separation instrument.

FIG. 28 is a plan view of the assembly of FIG. 27.

FIG. 29 is a perspective view of the assembly of FIG. 27 with a secondintermediate retractor assembly engaged to the first intermediateretractor assembly.

FIG. 30 is a plan view of the assembly of FIG. 29.

FIG. 31 a is an elevation view along the coronal plane of a humanskeleton.

FIG. 31 b is an elevation view along the sagittal plane of a humanskeleton.

FIG. 32 is a cross-sectional view through the lumbar region of a human.

FIG. 33 is a plan view of a vertebral endplate and an outline of animplant of an embodiment of the invention.

FIG. 34 is a plan view of a vertebral endplate and an outline of animplant of an embodiment of the invention.

DETAILED DESCRIPTION

FIGS. 1-4 illustrate an implant 1 with an elongated body positionable ina spinal disc space. A convexly curved upper surface 3 orientable towardan endplate of an upper vertebra and a convexly curved lower surface 5orientable toward an endplate of a lower vertebra are shown. In someembodiments, the upper and lower curvatures are mirror images of oneanother, or the curvatures may be different. For example, the uppercurvature may be greater than the lower curvature to better match a morepronounced curvature in the inferior endplate of a superior vertebra anda less pronounce curvature in the superior endplate of an inferiorvertebra. The upper surface 3 and lower surface 5 may have constantradii, may be compound curves, or may one or both be flat.

As shown in FIGS. 1-4, the upper and lower surfaces 3, 5 are broken by acavity 4. The cavity 4 may partially or fully penetrate the implant 1.In the illustrated embodiment, the upper surface 3 and the lower surface5 have portions on all sides of the cavity 4. Although in someillustrations, for clarity, the surfaces may only be labeled on a singleside, the surfaces are intended to include portions beyond each extentof the cavity 4. As shown, the upper surface 3 and the lower surface 5are convexly curved along an entire length of the body of the implant 1.The term “entire length” does not include various extensions ortruncations near the ends of the implant 1 in some embodiments. In otherembodiments of the invention, curves may be convex for only portions ofthe length, or other shapes may be interspersed between convex portions,or an overall convex shape may be formed by flat or variously shapedsegments to generate and overall convex shape.

A leading end portion 7 and an opposite trailing end portion 9 are alsoshown in FIGS. 1-4. The leading end portion 7 illustrated has a roundednose between the upper surface 3 and the lower surface 5. The nose onthe leading end shown is also partially rounded between an anteriorsidewall 10 and a posterior sidewall 11. In some embodiments, the nosemay be completely rounded between the sidewalls, or in others mayinclude flat portions. The illustrated trailing end portion 9 is planarand extends between the anterior and posterior sidewalls 10, 11. Inother embodiments, the trailing end portion may be curved, angular, orany other functional shape.

The anterior sidewall 10 extends between the leading end portion 7 andthe trailing end portion 9, and the anterior sidewall 10 shown is atleast partially convexly curved. As illustrated in FIG. 1, the anteriorsidewall 10 is defined by a maximally anterior portion 10 c, a firstcurved portion 10 a extending between the leading end portion 7 and themaximally anterior portion 10 c, and a second curved portion 10 bextending between the trailing end portion 9 and the maximally anteriorportion 10 c. As shown, the first and second curved portions 10 a, 10 bare convex curves, and the maximally anterior portion 10 c is a flatsegment. In other embodiments, the first and second curved portions 10a, 10 b may be a part of the same convex curve and the maximallyanterior portion 10 c may be a point along the curve. Alternatively,there may be only one of the first and second curved portions 10 a, 10 bcomposing the anterior sidewall 10, or the sidewall may be a combinationof segments of various shapes. In some embodiments, the convex curve ofthe anterior sidewall 10 will include more than rounded corners orchamfers.

In some embodiments, the curvature of the anterior sidewall 10 is usefulto permit the implant 1, and particularly first and second curvedportions 10 a, 10 b, to be substantially located between the corticalrims of the supported vertebrae without extending beyond the bounds ofthe cortical rims. Referring to FIG. 33, a cortical rim 610 extendsaround the periphery of an anterior portion of an inferior vertebralbody V. Because first and second curved portion 10 a, 10 b are curved,the implant 1 is capable of being positioned more anteriorly and morealong the cortical rim 610. The cortical rim 610 provides more supportthan the interior, cancellous bone 620 of the vertebral body V. Analternate placement for an implant is illustrated in FIG. 34. Analternate implant 601 is shown placed from a lateral approach, butplaced more posteriorly on the vertebral body V.

The posterior sidewall 11 shown extends between the leading end portion7 and the trailing end portion 9 of the implant 1. The body of theimplant 1 includes a height between the upper and lower surfaces 3, 5corresponding to a desired disc space height between the upper vertebraendplate and the lower vertebra endplate. The term “height” refers to adistance between the upper and lower surfaces 3, 5. In some embodiments,the upper and lower surfaces 3, 5 are not planar and are not a constantdistance from one another. Therefore, the term height is not limited toa specific distance, but may be used to describe an overall shape thatproduces a desired separation of the vertebrae.

In some embodiments, at least one of the upper surface 3 and the lowersurface 5 are curved such that the height of the implant 1 near itscenter is greater than the height of the implant 1 near its leading endportion 7. For an implant such as implant 1 that includes a lordoticconfiguration, the height of the implant near its center is the maximumheight of the implant near its center. As shown in FIGS. 1-4, the heightis the height of the anterior sidewall 10 near its center. For animplant such as non-lordotic implant 101 (FIG. 5), the height of theimplant near its center is the height of either the anterior sidewall110 or the posterior sidewall 111 near either of their centers. Forexample, the height of the non-lordotic implant 101 (FIG. 5) near itscenter is labeled as h_(i). The height of the implant 1 near its leadingend portion 7 is the maximum distance between the upper surface 3 andthe lower surface 5 prior to any rounded or pointed portions of theleading end portion 7 such as a nose. For example, the height of thenon-lordotic implant 101 (FIG. 5) near its leading end portion islabeled as h_(n).

The height of an implant of embodiments of the invention near the centerof the implant is between about 7 mm and 19 mm, and the height of suchan implant near the leading end is at least about 3 mm less than theheight of the respective implant near its center. For example, animplant with a height of 12 mm near its center would have a height of 9mm or less near its leading end. In another specific embodiment, theheight of an implant near its center is between about 13 mm and 19 mm,and the height of the implant at its leading end is between about 4 mmand 9 mm. For another embodiment, the height of an implant near itscenter is between about 9 mm and 13 mm, and the height of the implant atits leading end is between about 4 mm and 7 mm. In yet anotherembodiment, the height of an implant near its center is between about 6mm and 9 mm, and the height of the implant at its leading end is betweenabout 3 mm and 5 mm. In still another embodiment, the height of animplant of embodiments of the invention near the center of the implantis between about 8 mm and 14 mm, and the height of such an implant nearthe leading end is at least about 3 mm less than the height of therespective implant near its center.

The leading end portion 7 of some embodiments of the invention isstructured for insertion into the disc space in an at least partiallycollapsed condition. The height of the implant 1, including the leadingend portion 7 in such embodiments is sized to restore the collapsed discspace to the desired disc space height as the body is inserted in thecollapsed disc space. The leading end portion 7 may facilitate insertiondue to a relatively short height, and an increasing height along thelength of the implant 1 will restore the collapsed disc space.

As illustrated in FIGS. 1-4, an average height of the anterior sidewall10 is greater than an average height of the posterior sidewall 11. Whenimplanted by some methods, this facilitates the implant 1 providinglordotic correction between vertebrae. FIGS. 33 and 34 show placementsof devices that would create lordotic correction for an implant with ananterior sidewall of greater average height than its posterior sidewall.In other embodiments, the anterior and posterior sidewalls may be thesame height, or the posterior sidewall may be of greater height in partor on average. A posterior wall of greater height could be useful inportions of the spine where a kyphotic curvature is desirable, tocorrect a deformity, or to provide treatment for a traumatic injury.

The implant 1 may include a number of engagement members 15 along itupper surface 3 and/or lower surface 5. The engagement members 15 shownin FIGS. 1-4 project outwardly from the upper and lower surfaces 3, 5 toengage bony tissue of the adjacent vertebral endplate when the implant 1is positioned in the spinal disc space. The engagement members 15illustrated are a number of teeth along the cavity 4 that are rakedtoward the direction of implant insertion. Engagement members 15 may beteeth or other projections or voids that create some resistance tomovement, including such elements as a friction coating or frictionsurface treatment. The engagement members 15 illustrated are rakedtoward the direction of implant insertion to resist expulsion of theimplant through the insertion incision with less resistance toinsertion, but the engagement members may be configured to resistmovement in any direction.

As shown in FIGS. 2 and 3, the implant 1 includes a first notch 16 inthe anterior sidewall 10, and a second notch 18 in the posteriorsidewall 11. The illustrated first and second notches 16, 18 have flatupper and lower surfaces, but the notches may be of any configurationthat facilitates gripping of the implant 1 with a coupling member. Thecoupling member may include some or all of the elements of the insertioninstrument 550 (FIG. 8) or other such devices. The coupling member mayhave first and second fingers 568, 570 positionable in respective onesof the first and second notches 16, 18 to secure the body of the implant1 to the coupling member. In some embodiments, the coupling member isincorporated with the implant 1 for insertion into the disc space. Asecuring mechanism 19 is incorporated in some embodiments of theinvention. The securing mechanism 19 may be a threaded hole forreceiving a threaded shaft or screw. The securing mechanism may also beconfigured to provide an interference fit or any other device forengagement with a coupling member to facilitate connection with thecoupling member.

Referring to FIG. 5, another embodiment of an implant of the inventionis illustrated. The non-lordotic implant 101 has an anterior sidewall110 and a posterior sidewall 111 that are substantially the same height.Such an implant may be useful to provide vertebral spacing in clinicalcircumstances where lordotic correction is not necessary. Other featuresand configurations of the non-lordotic implant 101 are similar to thefeatures and configurations of the implant 1 described above.

Another embodiment of the invention is illustrated in FIGS. 6 and 7. Asymmetrical implant 201 has an elongated body positionable in a spinaldisc space. A convexly curved upper surface 203 orientable toward anendplate of an upper vertebra and a convexly curved lower surface 205orientable toward an endplate of a lower vertebra are shown. In someembodiments, the upper and lower curvatures are mirror images of oneanother, or the curvatures may be different. For example, the uppercurvature may be greater than the lower curvature to better match a morepronounced curvature in the inferior endplate of a superior vertebra anda less pronounce curvature in the superior endplate of an inferiorvertebra. The upper surface 203 and lower surface 205 may have constantradii, may be compound curves, or may one or both be flat.

As shown in FIG. 7, the upper and lower surfaces 203, 205 are broken bya cavity 204. The cavity 204 may partially or fully penetrate thesymmetrical implant 201. In the illustrated embodiment, the uppersurface 203 and the lower surface 205 have portions on all sides of thecavity 204. Although in some illustrations, for clarity, the surfacesmay only be labeled on a single side, the surfaces are intended toinclude portions beyond each extent of the cavity 204. As shown, theupper surface 203 and the lower surface 205 are convexly curved along anentire length of the body of the symmetrical implant 201. The term“entire length” does not include various extensions or truncations nearthe ends of the symmetrical implant 201 in some embodiments. In otherembodiments of the invention, curves may be convex for only portions ofthe length, or other shapes may be interspersed between convex portions,or an overall convex shape may be formed by flat or variously shapedsegments to generate and overall convex shape.

A first end portion 207 and an opposite second end portion 209 are alsoshown in FIGS. 6 and 7. The symmetrical implant 201 is capable ofinsertion with either the first or second end portions 207, 209 beinginserted into the disc space first. Likewise, either the first or secondend portions 207, 209 may be coupled to an insertion instrument.Surgeons may at different times want to approach patients from the leftor right side. An implant configured symmetrically may be useful, foramong other purposes, to reduce inventory where implants are requiredwith differently shaped upper and lower surfaces 203, 205.

The anterior sidewall 210 and posterior sidewall 211 configurations aresimilar to the anterior sidewall 10 and posterior sidewall 11 describedin detail above and all features may be applied to any embodiment.

The first and second end portions 207, 209 of some embodiments of theinvention are structured for insertion into the disc space in an atleast partially collapsed condition. The height of the symmetricalimplant 201, including the end portion inserted, is sized to restore thecollapsed disc space to the desired disc space height as the body isinserted in the collapsed disc space. The end portion inserted mayfacilitate insertion due to a relatively short height, and an increasingheight along the length of the implant 201 will restore the collapseddisc space.

The symmetrical implant 201 may include a number of engagement members215 along it upper surface 203 and/or lower surface 205. The engagementmembers 215 shown in FIG. 6 project outwardly from the upper and lowersurfaces 203, 205 to engage bony tissue of the adjacent vertebralendplate when the symmetrical implant 201 is positioned in the spinaldisc space. The engagement members 215 illustrated are a number of teethalong the cavity 204. Engagement members 215 may be teeth, includingraked teeth, or other projections or voids that create some resistanceto movement, including such elements as a friction coating or frictionsurface treatment. The engagement members may be configured to resistmovement in any direction.

As shown in FIG. 7, the symmetrical implant 201 includes a first notch216 in the anterior sidewall 210, and a second notch 218 in theposterior sidewall 211 at both the first end portion 207 and the secondend portion 209. The illustrated first and second notches 216, 218 haveflat upper and lower surfaces, but the notches may be of anyconfiguration that facilitates gripping of the implant 1 with a couplingmember. The coupling member may include some or all of the elements ofthe insertion instrument 550 (FIG. 8) or other such devices. Thecoupling member may have first and second fingers 568, 570 positionablein respective ones of the first and second notches 216, 218 to securethe body of the symmetrical implant 201 to the coupling member. In someembodiments, the coupling member is incorporated with the symmetricalimplant 201 for insertion into the disc space. A securing mechanism 219is incorporated in some embodiments of the invention. The securingmechanism 219 may be a threaded hole for receiving a threaded shaft orscrew. The securing mechanism may also be configured to provide aninterference fit or any other device for engagement with a couplingmember to facilitate connection with the coupling member.

Referring to FIG. 8, there is shown an insertion instrument 550.Insertion instrument 550 includes an elongated shaft 552 extendingbetween a proximal portion 554 and a distal gripping portion 556 thatserves as a coupling member to couple an implant such as the implant 1to shaft 552. Proximal portion 554 includes a handle 558 extendingtransversely to shaft 552. In one embodiment, handle 558 is obliquelyoriented to shaft 552 to facilitate manipulation and gesturing withinsertion instrument 550. Shaft 552 projects proximally from handle 558to a housing portion 560. Housing portion 560 includes an adjustmentmember 562 housed therein. An inner shaft 564 (FIG. 9) extends distallyfrom adjustment member 562 and through shaft 552 to distal grippingportion 556. Adjustment member 562 provides a thumbwheel or othersuitable gripping element to facilitate the surgeon rotating inner shaft564 within outer shaft 552 for engagement of the distal end of innershaft 564 with an implant.

Distal gripping portion 556 includes a body member 566 and a pair offingers 568, 570 extending distally from opposite sides of body member566. The distal end of inner shaft 564 projects distally from the bodymember 566 and is centrally located between fingers 568, 570. As shownin FIG. 10, fingers 568, 570 are positionable in respective ones of thenotches of the implant to which insertion instrument 550 is engaged,such as implant 1 in the illustrated embodiment. Inner shaft 564 isengageable in the bore in the proximal end wall of implant, such as bore328 of implant 310. The outer surfaces of fingers 568, 570 are flush orrecessed relative to the outer lateral surfaces of sidewalls of theimplant such that fingers 568, 570 do not protrude beyond the sidewallsof the implant 1. When engaged to the implant 1, fingers 568, 570 definean overall width that is less than the width of the implant between theouter lateral surfaces of its sidewalls. This minimizes the insertionprofile of the implant and instrument assembly, and facilitates a lessinvasive approach to the spinal disc space.

Referring to FIG. 11, there is shown another embodiment insertioninstrument 580. Insertion instrument 580 includes an outer shaft 582longitudinally movable about an inner shaft 584. Insertion instrument580 includes a distal gripping portion 586 that forms a coupling memberfor coupling an implant to inner shaft 584. Distal gripping portion 586includes a body member at a distal end of inner shaft 584 that includesa base portion 598 and a pair of biasing members 588, 590 separated by acentral slot 596. Biasing members 588, 590 are coupled to one anotherabout a living or integral hinge formed at base portion 598. Fingers592, 594 extend distally from respective ones of the biasing members588, 590. Base portion 598 includes a proximally tapered outer surfaceprofile. Outer shaft 582 is movable distally relative to inner shaft 584and along the outer surface profile of at least base portion 598 to movebiasing members 588, 590 and thus fingers 592, 594 toward one another togrip an implant therebetween. The implant can be released by proximallydisplacing outer shaft 582 relative to inner shaft 584 to allow biasingmembers 588, 590 and thus fingers 592, 594 to move away from one anothertoward their normal state.

Various mechanisms for moving outer shaft 582, 584 are contemplated. Forexample, shafts 582, 584 can be threadingly engaged to one another andouter shaft 584 is rotated about inner shaft 582 to effect proximal anddistal movement therebetween. In another example, proximal handleactuators are coupled to inner and outer shaft 582, 584, and the handleseffect proximal and distal linear movement between the shafts as thehandles are manipulated. Other suitable mechanisms for moving the innerand outer shafts longitudinally relative to one another are alsocontemplated.

Referring to FIG. 12, a graft implant 301 is illustrated with anelongated body positionable in a spinal disc space. The embodiment has aconvexly curved upper surface 303 orientable toward an endplate of anupper vertebra, a convexly curved lower surface 305 orientable toward anendplate of a lower vertebra, a leading end portion 307, and an oppositetrailing end portion 309. An at least partially convexly curved anteriorsidewall 310 extends between the leading end portion 307 and thetrailing end portion 309, and a posterior sidewall 311 extends betweenthe leading end portion 307 and the trailing end portion 309. The graftimplant 301 includes a height between the upper and lower surfaces 303,305 corresponding to a desired disc space height between the uppervertebra endplate and the lower vertebra endplate. The leading endportion 307 is structured for insertion into the disc space in an atleast partially collapsed condition and the height is sized to restorethe collapsed disc space to the desired disc space height as the graftimplant 301 is inserted in the collapsed disc space.

The graft implant 301 shares configurations, functions, and descriptionswith the implant 1 described in detail above. Additionally, embodimentsof the graft implant 301, and other embodiments described herein, may beconstructed of bone graft materials. Without limitation, the bone graftmaterial may be allograft bone. In some embodiments, the graft implant301 is constructed of a solid section of bone. In other embodiments, thegraft implant 301 is constructed of planks of bone that are assembledinto a final configuration. The graft implant 301 may be constructed ofplanks of bone that are assembled along horizontal or vertical planesthrough one or more longitudinal axes of the graft implant 301. In someembodiments, a cavity is cut or constructed through the graft implant301. The cavity may be useful to contain grafting materials.

Embodiments of the implant include a device with an upper surface means,a lower surface means, a leading end means, an opposite trailing endportion, and an at least partially convexly curved anterior sidewallmeans. The trial bodies of the trial instruments and the implant bodiescan be made from any biocompatible material, including synthetic ornatural autograft, allograft or xenograft tissues, and can be resorbableor non-resorbable in nature. Examples of tissue materials include hardtissues, connective tissues, demineralized bone matrix and combinationsthereof. Further examples of resorbable materials are polylactide,polyglycolide, tyrosine-derived polycarbonate, polyanhydride,polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite,bioactive glass, and combinations thereof. Further examples ofnon-resorbable materials are non-reinforced polymers, carbon-reinforcedpolymer composites, PEEK and PEEK composites, shape-memory alloys,titanium, titanium alloys, cobalt chrome alloys, stainless steel,ceramics and combinations thereof and others as well. If the trialinstrument or implant is made from radiolucent material, radiographicmarkers can be located on the trial instrument or implant to provide theability to monitor and determine radiographically or fluoroscopicallythe location of the body in the spinal disc space. The materialcomprising the trial bodies can be solid, porous, spongy, perforated,drilled, and/or open.

There is contemplated an implant for insertion into a spinal disc spacebetween adjacent vertebrae. The implant can be impacted or pushed intothe disc space. The implant can be provided with a distal end or leadinginsertion end that is sized for insertion into the collapsed disc space.As the implant is inserted, the implant can restore the collapsed discspace to a desired disc space height. The desired disc space heightcorresponds to the height of the implant proximal the distal end. Onceinserted, the implant can maintain the disc space at the desired discspace height.

There is further contemplated an implant that, when inserted, restoresand maintains a desired disc space height of a collapsed disc spacebetween an upper vertebra and a lower vertebra. The implant includes abody with a distal end, a proximal end, an upper surface orientabletoward an endplate of the upper vertebra and a lower surface orientabletoward an endplate of the lower vertebra. The body of the implant has afirst height between the upper and lower surfaces corresponding to thedesired disc space height. The body of the implant also has a secondheight at its distal end that is less than a height of the collapseddisc space.

It is contemplated that the implants can be provided with bi-convexcurvature of the upper and lower surfaces, allowing the implants tocenter in the endplates of the disc space. It is further contemplatedthat the upper and lower surfaces of the implant can be planar orinclude compound geometry. The upper and lower surfaces of the implantcan also be configured to establish lordotic or kyphotic angulationbetween the adjacent vertebral bodies.

It is contemplated that an insertion instrument can be engaged tolateral walls of an intervertebral implant. The insertion instrumentincludes a distal coupling portion positionable in notches formed incorresponding ones of the lateral walls of the implant. The couplingportion has a first position engaging the implant in the notches and asecond position disengaged from the implant in the notches. The width ofthe coupling portion in each of its first and second positions is lessthan the width of the implant between the lateral walls of the implant.

An embodiment of the invention is a system for placing an implantbetween an endplate of an upper vertebra and an endplate of a lowervertebra that includes a trial instrument set and an implant. Theimplant of the system may include any implant described above, such asimplant 1, non-lordotic implant 101, symmetrical implant 201, or graftimplant 301, or any other implant compatible with the system set forthherein.

In FIG. 13 there is shown a trial instrument set 50 having a number oftrial instruments 52, 54, 56, 58, 60, 62, 64, 66, 68 and 70. Trialinstrument 52 includes a handle 52 a, a shaft 52 b extending distallyfrom handle 52 a, and a trial body 52 c. Each of the other trialinstruments also includes a handle, a shaft and a trial body. It iscontemplated that each trial body of the trial instruments provides adifferent height between an upper and a lower contact surface thereoffor restoring a collapsed disc space. As used herein, the term “trialinstrument” with reference to the size or shape of the trial instrumentmay include the size or shape of the trial body. Trial instrument 52 canbe provided with a trial body having the smallest height H of theinstrument set 50, and trial instrument 70 can be provided with a trialbody having the largest height H′ of the instrument set 50. Theremaining trial instruments can provide a number of different heighttrial instruments ranging in height between H and H′. In one particularembodiment of instrument set 50, the height of the trial instruments inthe set increase in one millimeter increments. In another particularembodiment, the heights range from 6 millimeters to 19 millimeters inone millimeter increments. Other increments and other ranges of heightsare also contemplated.

An embodiment of the trial instrument set 50 has at least twoinstruments of different sizes. Instruments of the trial instrument set50 may have an upper surface orientable toward the upper vertebra, alower surface orientable toward the lower vertebra, and a leading endportion with segments that diverge from the leading end to meet theupper surface and the lower surface respectively.

Instruments of the trial instrument set 50 may have upper and/or lowersurfaces with convex curvatures and may have a curve extending betweentheir upper and lower surfaces. The curve extending between the upperand lower surface may be a radius or any other functional shape whethera curve is incorporated or not. In some embodiments, at least one of thetrial instruments of the trial instrument set 50 is substantially thesame shape as an implant of the system. At least one of the trialinstruments of the trial instrument set 50 may be substantially the sameshape as an implant of the system about either a horizontal or verticalplane of the implant, or about both planes.

The system may also include an access portal insertable through anincision. Such an access portal may provide a path through which a trialinstrument, an implant, or both may be passed. The access portal may bea tubular port, a retractor, or any other mechanism for holding open anoperative site. A tubular port 170 is shown in FIG. 14 e. A retractorstructure 180 is illustrated in FIG. 14 f, and various embodiments aredescribed in association with FIGS. 15-30.

Referring to FIGS. 15 and 16, there is shown an embodiment of aretractor 320. Retractor 320 includes a first retractor portion 322 anda second retractor portion 342. First portion 322 includes a body 323extending between a distal end 324 and an opposite proximal end 326.Second portion 342 includes a body 343 extending between a distal end344 and an opposite proximal end 346. Distal ends 324, 344 can bebeveled or distally tapered to facilitate insertion, althoughnon-beveled ends are also contemplated. First portion 322 can bepositioned adjacent to or mated with second portion 342 along adjacentones of the longitudinal edges 325, 327 of first portion 322 andlongitudinal edges 345, 347 of second portion 342. Other arrangementsbetween the adjacent edges are also contemplated as discussed above. Itis further contemplated that the longitudinal edges can be spaced fromone another in the insertion configuration. A working channel 350 isformed between first portion 322 and second portion 342. Working channel350 extends between and opens at distal ends 324, 344 and proximal ends326, 346.

Retractor 320 is insertable through skin and tissue of a patient toprovide working channel 350 to the surgical site. It is contemplatedthat retractor 320 is inserted through the skin and tissue in aninsertion configuration for working channel 350, such as shown in FIGS.15-18. In the insertion configuration, working channel 350 issubstantially enclosed or circumscribed by first portion 322 and secondportion 342. After insertion into the patient, working channel 350 canbe enlarged by separating first portion 322 and second portion 342 awayfrom one another along an axis 321 extending therebetween. Separation offirst and second portions 322, 342 increases the size of working channel350 from proximal ends 326, 346 to distal ends 324, 344. The firstportion 322 and the second portion 342 may also include couplingstructures (not shown) for coupling to at least one structure near asurgical site. A fastener, such as a bone screw, may be used to couplebetween either or both the first portion 322 and the second portion 342and the structure near the surgical site. The coupling could be madebefore or after separation of the first and second portions 322, 342.

In the insertion configuration of FIGS. 15-18, working channel 350 iscircumscribed or substantially enclosed by first portion 322 and secondportion 342. Bodies 323 and 343 can be configured as discussed abovewith respect to the bodies of the portions of retractor 20. Workingchannel 350 can have a size in the insertion configuration that allowspassage of one or more surgical instruments and/or implants to thesurgical location in the patient's body, although smaller sizes are alsocontemplated. It may be desirable during surgery to provide greateraccess to the location in the patient's body beyond the locationsprovided through working channel 350 in its insertion configuration.Accordingly, first portion 322 and second portion 342 are movable awayfrom one another along axis 321 to enlarge working channel 350.

First portion 322 includes body 323 with a semi-cylindrical shapeextending between distal end 324 and proximal end 326. A collar 328extends about proximal end 326, and forms a lip extending about theouter surface of body 323. Second portion 342 includes body 343 having asemi-cylindrical shape extending between distal end 344 and proximal end346. A collar 348 extends about proximal end 346 of second portion 342,and defines a lip extending about the outer surface of body 343. It isfurther contemplated that first and second portions 322, 342 can beprovided with or without a collar and/or a lip. First and secondportions 322, 342 can also be provided with bracket members forengagement with an external arm that supports retractor 320 whilepositioned in the patient.

Extending from collar 328 of first portion 322 is a first engagementstructure 332 having a head portion 336 forming a recess 333 therein.Extending from collar 348 of second portion 342 is a second engagementstructure 352 having a head portion 356 forming a recess 353 therein.Engagement structures 332, 352 can be integrally formed with orremovably engaged to the respective collars 328, 348. As discussedfurther below, an instrument for separating first portion 322 and secondportion 342 can be non-releasably or releasably engaged to engagementstructures 332, 352 for application of a separation force to enlargeworking channel 350 by separating first portion 322 and second portion342. Such an instrument could also be releasably or non-releasablyengaged to first portion 322 and second portion 342. Engagementstructures 332, 352 extend laterally from portions 322, 342 tofacilitate allow engagement of a separation instrument to engagementstructures 332, 352 without obstructing working channel 350 with theseparation instrument. Such an instrument could also maintain firstportion 322 and second portion 342 in the initial insertionconfiguration during and after insertion. The separation instrument canalso maintain the enlarged configuration for working channel 350 insitu.

Recesses 333, 353 are adapted to receive engagement arms of theseparation instrument engageable to portions 322, 342. In theillustrated embodiments, engagement structures 332, 352 extend laterallyfrom and project proximally above the respective collar 328, 348.Engagement structures 332, 352 extend alongside one another and abut oneanother when portions 322, 342 are in their insertion configuration.Other configurations for the engagement structures are alsocontemplated, including engagement structures that are non-linear, thatextend in directions away from one another when portions 322, 324 are intheir insertion configuration, and engagement structures that do notabut one another in the insertion configuration.

Recesses 333, 353 open laterally to receive respective ones of theengagement arms of the separation instrument. Recess 333 includes akeyway opening 335 and a receptacle 337 in communication with opening335. Receptacle 337 is enlarged relative to opening 335, and is shapedto receive a portion of the engagement arm of the separation instrumentpositioned therein. Similarly, recess 353 includes a keyway opening 355and a receptacle 357 in communication with opening 355. Receptacle 357is enlarged relative to opening 355, and is shaped to receive a portionof the engagement arm of the separation instrument positioned therein.Openings 335, 355 and receptacles 337, 357 are open along the proximalsides of the respective engagement structures 332, 352 to facilitateplacement of the separation instrument engagement arms therein. Otherconfigurations for the recess 333, 353 are also contemplated, includingrecesses that are enclosed, uniform, or any other suitable configurationto receive a at least a portion of an engagement arm. Still otherembodiments contemplate that engagement structures 332, 352 do notinclude recesses, but rather are shaped for receipt in or otherwiseengage the respective engagement arm of the separation instrument.

As shown in FIGS. 19 and 20, alignment members 330 can be provided alongone side of one of the engagement structures 332, 352 (engagementstructure 352 in the illustrated embodiment.) In the illustratedembodiment, alignment members 330 are rounded protrusions which arereceived in holes provided in the adjacent side of the other engagementstructure 332, 352 when engagement structures 332, 352 are positionedadjacent one another. Alignment members 330 maintain first portion 322and second portion 342 in longitudinal alignment with one another duringand after insertion. Other embodiments contemplate other arrangementsfor aligning and/or releasably coupling first portion 322 and secondportion 342 to one another. Examples of such arrangements includedovetail connections, fasteners, threaded coupling members, clampingmembers, snap rings, compression bands, straps, ball-detent mechanisms,and releasably interlocking cams or tabs, for example.

Referring to FIGS. 17-20, there is shown a separation instrument 360operable to move first and second portions 322, 342 away from oneanother to enlarge working channel 350. It is contemplated thatseparation instrument 360 includes a lateral separator operable tolinearly move first and second retractor portions away from one anotheralong axis 321. It is further contemplated that separation instrument360 includes at least one rotational separator to pivotally move distalends of first and second portions 322, 342 away from one another alongaxis 321. The lateral and rotational separators can be selectivelyemployed by the surgeon during the surgical procedure to enlarge workingchannel 350 and provide the tissue retraction desired for conducting thesurgical procedure through working channel 350. Enlargement of workingchannel 350 can further retract tissue away from the surgical sitedistal of the distal ends of retractor portions 322, 342 to providegreater access to tissue, bony structures, and other anatomical spaceslocated distally of retractor 320.

Separation instrument 360 includes a first connection assembly 362movably coupled with a second connection assembly 364. First connectionassembly 362 is further coupled to first portion 322, and secondconnection assembly 364 is coupled to second portion 342. First andsecond connection assemblies 362, 264 extend away from first and secondportions 322, 342 and away from the proximal end opening of workingchannel 350 to facilitate access to working channel 350 during thesurgical procedure. First and second connection assemblies 362, 364 areoperable to move first and second portions 322, 342 toward and away fromone another to separate tissue. First and second connection assemblies362, 364 further include lever assemblies 369, 389, respectively, thatare operable to rotate first and second portions 322, 342 about theirproximal ends to move their distal ends away from one another.

First connection assembly 362 includes a first engagement arm 372coupled to first engagement structure 332 of first portion 322 and afirst extension arm 366 extending from first engagement arm 372. Acoupling arm 368 is transversely oriented to and extends from the end offirst extension arm 366 opposite first engagement arm 372. A bracketmember 376 extends from coupling arm 368, and is engageable by aflexible arm mounted to a surgical table, for example. First connectionassembly 362 further includes a first intermediate member 367 fixedlycoupled to first extension arm 366. First engagement arm 372 isrotatable relative to intermediate member 367. A first mounting member375 extends from first engagement arm 372. A first lever arm 374 ispivotally mounted to first mounting member 375 and is movable between alocking position, such as shown in FIG. 17, to a pivoting position, asshown FIG. 21.

Similarly, second connection assembly 364 includes a second engagementarm 394 coupled to second engagement structure 352 of second portion 342and a second extension arm 392 extending from second engagement arm 394.A housing 390 extends from the end of second extension arm 392 oppositesecond engagement arm 394. Housing 390 includes a passage through whichcoupling arm 368 is movably received. An adjustment mechanism 399mounted to housing 390 is engageable to coupling arm 368 and operable totranslate coupling arm 368 in housing 390 to effect movement of firstand second portions 322, 342 toward and away from one another alongtranslation axis 321.

In the illustrated embodiment, coupling arm 368 includes a number ofratchet teeth 370 formed therealong, which are engageable by adjustmentmechanism 399. Adjustment mechanism 399 includes a gear wheel 400 withteeth that interdigitate with teeth 370 to effect movement of couplingarm 368 in housing 390 as handle 398 is rotated. A locking mechanism 402is spring-biased into engagement with teeth 370, and maintainsseparation of first and second portions 322, 342 when handle 398 isreleased. Locking mechanism 402 can also be depressed to pivot itsengagement end out of engagement with teeth 470 and allow first andsecond portions 322, 342 to move toward one another.

Second connection assembly 364 further includes a second intermediatemember 393 fixedly coupled to second extension arm 392. Secondengagement arm 394 is rotatable relative to intermediate member 393. Asecond mounting member 397 extends from second engagement arm 394alongside second intermediate member 393. Second lever arm 396 ispivotally mounted to second mounting member 397 and is movable between alocking position, such as shown in FIG. 17, to a pivoting position, asshown FIG. 21. Intermediate members 367, 393 can be provided as separatecomponents, or can be integral with the respective extension arm.

As shown in FIGS. 23-24, first and second engagement arms 372, 394include feet 378, 404, respectively. Feet 378, 404 are slidably andremovably received in respective ones of the recesses 333, 353 ofengagement structures 332, 352. In the illustrated embodiment, feet 378,404 include an enlarged outer end portion 379, 405 and a smallercross-section intermediate transition portion 381, 407 extending betweenengagement arms 372, 394 and the enlarged outer end portion 379, 405.Intermediate transition portions 381, 407 are received in theintermediate keyway openings 335, 355, and enlarged outer end portions379, 405 are received in receptacles 337, 357.

Feet 378, 404 are received in recesses 333, 353 (FIG. 15) in such amanner that, as discussed further below, lever arms 374, 396 can effectpivoting of first and second retractor portions 322, 342 by rotatingengagement arms 372, 394 about their respective axes 371, 391,respectively. Furthermore, separation instrument 360 can be easilyremoved from first and second retractor portions 322, 342, facilitatingclean-up of the instrument assembly after the surgical procedure. It isalso contemplated that disposable first and second portions 322, 342 maybe used, or that a set of first and second portions 322, 342 can beprovided in various lengths, shapes and/or sizes from which a surgeonmay select and employ with separation instrument 360.

Intermediate members 367, 393 each include a locking portion, such asengagement portions 426, 414 shown in FIGS. 24, 26, that is engageablewith a respective one of the lever arm locking assemblies 420, 408.Lever arm locking assemblies 420, 408 each include a pawl 409, 421pivotally coupled to an adjacent one of the mounting members 375, 397.For example, as shown in FIGS. 24 and 26, lever arm locking assembly 420includes a pivot pin 422 mounted to mounting member 375 about which pawl421 can be pivoted. Similarly, lever arm locking assembly 408 includes apivot pin 410 mounted to mounting member 397 about which pawl 409 can bepivoted. Intermediate members 367, 393 each include respective ones ofengagement portions 426, 414 to which the locking members 420, 408 areengageable to maintain a pivoted position of first and second portions322, 342.

For example, as shown in FIG. 26 relative to intermediate member 367,there is provided an engagement portion 426 along intermediate member367 oriented toward pawl 421. Pawl 421 includes a proximal handleportion 423 and a distal engagement end 424. Distal engagement end 424is positionable in at least one the recesses provided between teeth 428to maintain a pivoted position of first portion 322. As lever arm 374 isrotated counterclockwise to pivot the distal end of retractor portion322 away from the distal end of retractor portion 342, pawl 421 movesabout engagement portion 426 for engagement there with at a locationcorresponding to the position of the pivoted retractor portion 322.

Other embodiments contemplate that intermediate members 367, 393 aremovable as the respective retractor portion is pivoted. In suchembodiments, the pawl 409, 421 does not move or rotate with rotation ofengagement arm, but rather remains fixed for engagement with theadjacent engagement portion of the respective intermediate member 367,393 as it is rotated.

In FIG. 24, first lever arm 374 is shown pivoted on mounting member 375to its pivoting position, and second lever arm 396 is shown pivoted onmounting member 397 to its locking position. In the locking position,lever arm 396 includes a protrusion 406 that is engageable to theproximal handle portion of pawl 409. In the engaged position, proximalhandle portion 413 cannot be moved toward mounting member 397 to removeits engagement end 412 from the teeth along engagement portion 414 ofintermediate member 393. Accordingly, the pivoted position of secondretractor portion 342 is locked by the positioning of lever arm 396 inits locking position, and second retractor portion 342 cannot be movedunless lever arm 396 is moved to its pivoting position.

In FIG. 24 first lever arm 374 is shown in its pivoting position, andincludes a protrusion 418 extending from first lever arm 374 that ispositioned out of contact with pawl 421. In this position, pawl 421 canbe pivoted about pin 422 to remove engagement end 424 from between teeth428. Lever arm 374 can then be manipulated to pivot first retractorportion 322 to a desired angular position along axis 321. As lever arm374 is pivoted, locking member 420 is moved therewith into alignmentwith another space between teeth 428. When the desired orientation offirst portion 322 is obtained, then proximal handle portion 423 can bereleased, and locking member 420 can be spring biased or otherwise movedto engage engagement portion 426 and maintain the pivoted position offirst portion 322. Lever arm 396 can then be pivoted on mounting member375 to its locking position where protrusion 418 engages pawl 421 toprevent it from being released from engagement portion 426.

Referring to FIGS. 27-28, there is shown a first intermediate retractorassembly 450 engageable to separation instrument 360. Intermediateretractor assembly 450 includes a retractor blade 452 positionablebetween first and second retractor portions 322, 342 to retract and/ormaintain tissue from the working channel 350 in a direction transverseto axis 321. In one operative approach to the spine, retractor 320 isoriented so that retractor portions 322, 342 are movable along axis 321oriented in the direction of the central axis of the spinal column, andblade 450 is positioned medially or adjacent to the spinal columnrelative to the other retractor blade portions 322, 342. Other operativeorientations in the incisions for the retractor blades and retractorportions are also contemplated.

First intermediate retractor assembly 450 includes blade 452 extendingbetween a distal end 454 and a proximal end 456. As shown in FIG. 28,distal end 454 is curved away from the working channel 350, and can restupon bone or other tissue when positioned in the retracted incision.Blade 452 can include a flat profile between distal end 454 and proximalend 456, or include a convex curvature about its longitudinal axis oralong its longitudinal axis. Blade 452 can also be provided as a singlemember, or in one or more components movable relative to one another tolengthen or shorten blade 452.

A linking arm 458 is transversely oriented to and extends from proximalend 456 of blade 452. Opposite blade 452 there is provided an engagingportion in the form of first and second hook members 462, 464. Lowerhook member 464 can be positioned about coupling arm 368 of separationinstrument 360. Linking arm 458 has a length such that the pressure fromthe tissue at the incision against blade 452 firmly holds hook member464 against coupling arm 368. Upper hook member 462 can serve as ahandle to facilitate placement of lower hook member over coupling arm368 or removal of intermediate retractor assembly 450. Otherarrangements for securing blade 452 to coupling arm 368 are alsocontemplated, such as fasteners and interfitting components, forexample.

First intermediate retractor assembly 450 is further mountable by asecond intermediate retractor assembly 470, as shown in FIGS. 29 and 30.Second intermediate retractor assembly 470 includes a blade 472extending between a distal end 474 and a proximal end 476. Distal end474 and the blade portion extending therefrom can be configured asdiscussed above with respect to blade 452. A second linking arm 478extends from proximal end 476, and includes an engagement foot 480opposite blade 472. Engagement foot 480 is removably mountable tolinking arm 458 of first intermediate retractor assembly 450.

First linking arm 458 includes slotted holes 460 (FIGS. 27-28) extendingtherethrough adapted to receive pins (not shown) extending from a lowersurface of foot 480 of second linking arm 478. The pins can be providedwith enlarged heads positionable in the enlarged portions of slottedholes 460, and are slidable to the narrowed ends of the slotted holes460 so that the heads are captured in slotted holes 460. In theillustrated embodiment, the narrowed portions of the slotted holes 460extend opposite retractor blade 472 so that the pressure from the tissueabout the incision pushing against blade 472 maintains the pins of foot480 in the narrowed end portions of slotted holes 460.

Second linking arm 478 includes offset portions 486 extendingtransversely to first linking arm 458. Offset portions 486 are linked byan offset member 479 extending therebetween. Offset member 479 can beprovided with an arcuate profile to extend around the respectiveadjacent retractor portion 322, 342 so as to not obstruct access toworking channel 350. Retractor blade 472 can maintain tissue retractionand provide protection to tissue located along the side of the workingchannel opposite retractor blade 452. First and second intermediateretractor assemblies 450, 470 provide the surgeon with additionaloptions during the surgical procedure with regard to tissue retractionand protection that can be readily employed with separation instrument360 engaged to retractor 320.

In one surgical procedure, retractor 320 is engaged to separationinstrument 360 and inserted in an incision. Retractor 320 can beadvanced over one or more dilators dilating an incision, or directlyinto the incision. Separation instrument 360 is then operated tolinearly move retractor portions 322, 342 away from one another alongaxis 321 to enlarge working channel 350. One or both of the lever arms374, 396 can be moved to its pivoting position and manipulated to pivotthe respective retractor portion 322, 342. When the retractor portionhas been pivoted, the respective lever arms are moved to their lockingposition so that the protrusion extending therefrom engages the adjacentpawl 409, 421 to maintain the pawl in engagement with adjacentengagement portion 414, 426.

When the desired separation has been obtained, the surgeon has theoption to select first intermediate retractor assembly 450. Blade 452 ispositioned in the incision between the separated first and secondretractor portions 322, 342, and linking arm 458 is secured to couplingarm 368. The surgeon has the further option of selecting secondintermediate retractor assembly 470, and positioning blade 472 in theincision opposite blade 452. Linking arm 478 can then be secured tolinking arm 458. Further adjustment of the spacing and orientation ofretractor portions 322, 342 can be completed with separation instrument360 and/or lever arms 374, 396.

It is further contemplated that retractor portions 322, 342 need not beseparated from one another linearly, but are separated during thesurgical procedure only by pivoting one or both of them along axis 321.Once the working channel 350 provides the desired access, the surgeoncan remove bone, tissue, disc material, or other matter throughretractor 320. Implants, such as fusion devices, screws, plates, rods,artificial discs, bone growth material, and other repair devices ortherapeutic substances can be delivered through retractor 320 to thedesired site in the patient's body.

The system may also include a dilator configured to increase the size ofthe incision prior to positioning of the access portal in the incision.The dilator may include a set of dilators as illustrated in FIGS. 14a-f. A procedure that includes a use of dilators and other associatedequipment is described in the illustrated example.

The present embodiment permits a substantially lateral approach to thespine. It is understood that many aspects of the procedure can beperformed from other approaches to the spine, such as postero-lateral,mid-line or medial posterior, and anterior. A guidewire 150 can beadvanced through the skin and tissue into a disc space or vertebral bodyV. A small incision may be made in the skin to facilitate penetration ofthe guidewire through the skin. In addition, the guidewire, which may bea K-wire, may inserted under radiographic or image guided control toverify its proper positioning. It is, of course, understood that theguidewire 150 can be positioned at virtually any location in the spineand in any portion of a vertebra V.

One or more tissue dilators may then be advanced over the guidewire 150,as depicted in FIGS. 14 b and 14 c. Alternatively, the dilators can beadvanced through the incision without the aid of a guidewire, followedby blunt dissection of the underlying tissues. In the specificillustrated embodiment, a series of successively larger dilators 151,152 and 153 are concentrically disposed over each other and over theguidewire 150 and advanced into the body to sequentially dilate the softtissues. In a specific embodiment, the dilators have successively largerdiameters, ranging from 5 mm, to 9 mm to 12.5 mm for the largestdilator. Other dilator sizes are contemplated depending upon theanatomical approach and upon the desired size of the working channel.

In an embodiment of the invention, an over-dilator 154 (FIG. 14 d) isused in a final dilation step to provide additional dilation of thetissues furthest from the surgical without substantially increasing thedilation of the tissues adjacent to the surgical site. Such retractionmay be useful to enhance visualization of the surgical site and toprovide additional space to angulate and operated instrumentationwithout increasing manipulation of neural and vascular structures nearthe surgical site. In some embodiments, the over-dilator 154 couldremain in place as an access portal. In some embodiments, theover-dilator 154 is designed to prepare tissues for an additionaltubular port, a retractor, or some other structure for creating anaccess portal. The over-dilator 154 illustrated fits concentrically oversmaller dilators 150-153, and has a proximal end that is larger than itsdistal end. The illustrated device has a circular cross-section, but anyfunctional cross-section or combination of cross-sections iscontemplated.

As shown in FIG. 14 e, the tubular port 170 is advanced over the largestdilator 153. The dilators and guidewire 150 may then be removed, leavingin place the tubular port 170 to serve as an access portal. Similarly,as illustrated in FIG. 14 f, the retractor 180 is advanced over thelargest dilator 153. The dilators and guidewire 150 may then be removed,leaving in place the tubular port 170 to serve as an access portal.

With an access portal established, a working channel is formed betweenthe skin of the patient and a working space adjacent the spine. It isunderstood that the length of the access portal is determined by theparticular surgical operation being performed and the anatomysurrounding the working space.

In some embodiments, the tubular port 170 or retractor 180 are at leastinitially only supported by the soft tissue and skin of the patient.However, both the tubular port 170 and the retractor 180 includemounting structures for fastening to a flexible support arm 160, whichcan be of known design. The flexible support arm 160 may be mounted tothe tubular port 170 or the retractor 180 by way of a bolt and wing nut161, as shown in FIGS. 14 e and 14 f, although other fasteners are alsocontemplated. This flexible arm 160 can be mounted on the surgical tableand can be readily adjusted into a fixed position to provide firmsupport for the access portal. The flexible arm 160 is configurable sothat it can be contoured as required to stay clear of the surgical siteand to allow the surgeons adequate room to manipulate the variety oftools that would be used throughout the procedure. Various visualizationand illumination devices may also be attached to the tubular port 170and the retractor 180 to provide better access to the surgical site asdesired by the surgeon. Examples include but are not limited to, fiberoptic lighting, visualization tubes, endoscopes, microscopes and thelike.

There is further contemplated an instrument set having two or moreself-distracting trial instruments and at least one implant. The two ormore trial instruments each have a body with a leading insertion endsized for insertion into a collapsed disc space. The leading insertionends of each trial instrument are substantially the same in size andshape. Each trial instrument has a height proximal the leading insertionend that restores the collapsed disc space height to a height differentthan that of the other trial bodies. The at least one implant has aleading insertion end that is substantially the same in size and shapeas the leading insertion end of at least one of the trial bodies of thetrial instruments. The implant has a height proximal its leadinginsertion end that corresponds to the desired restored disc space heightprovided by the at least one trial instrument.

Also contemplated is a kit including a set of trial instruments, eachhaving a trial instrument at a distal end thereof. The trial bodies havea self-distracting leading end portion insertable in a collapsed spinaldisc space. The kit further includes a set of implants positionable inthe collapsed spinal disc space. Each implant has a body sized andshaped to correspond in size and shape to a respective trial instrument.The fit of each implant body in the spinal disc space is indicated tothe surgeon by the fit of the corresponding trial instrument. When atrial instrument provides a desired fit, the trial instrument is removedand the implant corresponding to the trial instrument is inserted intothe collapsed disc space in the location previously occupied by thewithdrawn trial instrument.

Referring to FIGS. 31 a, 31 b, and 32, elevation views along the coronalplane the sagittal plane, respectively, of a human skeleton arepresented. FIG. 32 shows a cross-sectional view through the lumbarregion of a human. A lateral surgical approach vector 600 terminatingbetween lumbar vertebral bodies L3 and L4 is illustrated. A ribcage 601and an iliac 603 of the skeleton are shown on either side of theapproach vector 600.

Method embodiments of the invention include surgically placing animplant between vertebral bodies from a generally lateral surgicalapproach. One generally lateral surgical approach is illustrated bylateral surgical approach vector 600. Variations of the lateral approachinclude, without limitation, posteriorly oblique and anteriorly obliquedeviations as well as deviations along the coronal plane. A deviation inthe coronal plane, including “tilting” the approach such that theapproach is not perpendicular to the longitudinal axis of the spine, maybe necessary to reach various spinal discs and/or to avoid certainskeletal and soft tissues of patient.

A patient would be positioned such that a coronal, operative side of thepatient is accessible. A patient may be placed on their side, back, orstomach to make such an access. The table or other structure on whichthe patient is placed may be tilted in any plane or elevated to provideaccess. In some situations, it is desirable to place a protrusionagainst a non-operative side of the patient to cause separation betweenthe ribcage 601 and the iliac crest of the patient on the operativeside. In effect, the patient is “bent around” the protrusion to open upthe operative side in such embodiments. An incision is made in theoperative side of the patient between the ribcage 601 and the iliac 603.An incision may be made with any effective device, including byinsertion of an initial insertion dilator. The initial insertion dilatormay be a guidewire 150 (FIGS. 14 a-f). An initial insertion dilator islocated between the vertebral bodies in an embodiment of the invention.In other embodiments, the initial insertion dilator could be located inone of the vertebral bodies or some other tissue region. Tissue may bedilated with a first concentric dilator that fits over the initialinsertion dilator to further open the incision. Variations of thisprocedure and additional effective procedures are described inassociation with FIGS. 14 a-f.

Embodiments of the invention include inserting a tubular port 170 (FIG.14 e) or a retractor structure 180 into the incision (FIG. 14 f). Thetubular port 170 or the retractor structure 180 provide an access portalto the surgical site. In some embodiments, the insertion of the tubularport 170 or the retractor structure 180 includes insertion over one ormore dilators. Operation of the retractor structure 180 may beaccomplished to further open the incision. Operation of the retractorstructure 180 is described extensively in association with FIGS. 15-30.In some embodiments, parts of the retractor structure 180 may beattached to one or more vertebral bodies with a fastener or othereffective device. Such attachment may assist with the application ofretraction forces between vertebral bodies and/or may stabilize therelative positioning of retractor structure 180 and the anatomy.

Removal of vertebral disc material to create an opening for the implantbetween the vertebral bodies may be accomplished with any tool capableremoving disc material. In some embodiments at least one of a pituitaryrongeur, a rotary shaver, a rasp, and a scraper are used. Suchinstruments may be hand operated or driven by a power source. Accordingto one method, the collapsed disc space is accessed, and an opening isformed in the annulus having a width corresponding to the width of thetrial bodies and/or implants. Disc material is removed through theannulus opening, and, if desired by the surgeon, manual roughening ofthe endplates is performed with a scraper or other suitable endplateroughening instrument.

In some embodiments, a trial instrument is inserted between thevertebral bodies. The function of the trial may be to evaluate the sizeof the disc space or to distract the height of the disc space. A surgeoncan also determine whether a trial instrument or implant provides adesired disc space height by tactile feedback of the inserted trialinstrument or implant, and also by visual inspection. It may bedesirable for the inserted trial instrument or implant body tosufficiently stretch the remaining annulus tissue to provide firmengagement between the upper and lower surfaces of the trial or implantbody and the adjacent vertebral endplates. Sufficient surface areacontact may be desirable to prevent or minimize post-operative movementof the adjacent vertebrae relative to the implant. By providing trialbodies and implant bodies of corresponding size and shape, and byinserting the trial bodies and implant bodies in a non-distracted discspace, the inserted trial or implant body may provide immediate feedbackto the surgeon of the desirability of the fit. If distraction weremaintained by, for example, a second distractor, feedback to the surgeonof the post-operative fit of the implant would not be reliable oravailable, if at all, until distraction were removed. As such, the trialbodies and implants can be employed without utilization of externaldistraction or distraction maintained in another disc space locationduring trial instrument and implant insertion. However, secondarydistraction can be used to at least partially maintain disc spacedistraction upon withdrawal of the implants and trial bodies can beemployed. For example, pedicle screws and a rod can be employed on thecontralateral side to at least partially maintain distraction obtainedwith a particular implant or trial instrument; however, use of the sameis not required. Further, the trial bodies provide an indication of thefit of the implant into the disc space location. Since the implant mayinclude a shape that corresponds to that of the trial instrument, thereis an immediate confirmation to the surgeon that the correspondingimplant will fit into the space occupied by the trial instrument.

The trial bodies and/or implants are then sequentially inserted and, ifnecessary, withdrawn through the annulus opening and into the discspace. Since the implants are self-distracting, it is not necessary tochisel, drill or otherwise form the vertebral endplates to receive theimplant, although such steps are not precluded. Consequently, fewersteps in the surgical procedure are necessary since requirements forbilateral distraction, external distraction, chiseling, drilling andreaming are eliminated. In addition, the lack of other instruments ordevices in the disc space facilitates visualization of the disc spacepreparation, trial instrument insertion, and/or implant insertion.Elimination of cutting instruments in the disc space also may improvethe safety of the procedure.

Minimally invasive techniques employing the trial instruments andimplants are contemplated. In any particular patient, the implants canbe inserted via any one or combination of posterior, postero-lateral,antero-lateral, transforaminal, far lateral and/or anterior approaches.Implant insertion can occur through a single pathway to a collapsedspinal disc space, or through multiple pathways to the collapsed discspace, or through multiple pathways to multiple levels of collapseddiscs of the spinal column. Since the implant, and trial instruments ifemployed, are inserted into the same disc space location from the sameapproach, the entire procedure for inserting an implant can be completedthrough one pathway. If a multiple pathway procedure is to be employed,the surgeon can complete implant insertion through one pathway beforecreating and moving to work in a second pathway.

Since distraction and implant insertion occur along the same pathway tothe collapsed disc space, the implants and trial instruments are suitedfor use in minimally invasive procedures which employ a retractor sleeveto provide a pathway to the collapsed disc space. Such retractor sleevescan employ any one or combination of an endoscopic viewing element inthe working channel, a microscopic viewing system over the proximal endof the retractor sleeve, fluoroscopic viewing, loupes, naked eye and/orimage guidance.

In accordance with certain method embodiments, an implant is insertedbetween the vertebral bodies. Any of the implant embodiments describedabove, as well as certain other implants, may be inserted as part of themethods described herein. The implants of some embodiments may beimpacted or pushed into the disc space. As a result, disruption to theannulus tissue and tissue approaching the collapsed disc space isreduced since the footprint of the implant in the disc space can be thesame as the footprint occupied in the implant's approach to the discspace. Also, by providing the implant with the same footprint as thetrial instrument, and by performing distraction and implant insertionthrough the same portal or pathway, no additional tissue dissectionand/or retraction is required to accommodate distraction of the discspace during implant insertion.

With reference to FIG. 33, an anteriorly placed implant 1 with an atleast partially curved anterior wall 10 is illustrated. In someembodiments, the act of inserting the implant 1 includes placing theimplant 1 anteriorly between vertebral bodies such that the first curvedportion 10 a and the second curved portion 10 b of the anterior sidewall10 are substantially located between a cortical rim of the uppervertebra and the cortical rim 610 of the lower vertebra. In someembodiments, the first curved portion 10 a and the second curved portion10 b may one or both be located between cortical rims of the upper andlower vertebrae. In other embodiments, the entire anterior wall 10 maybe located between cortical rims of the upper and lower vertebrae. Thedisclosed curvatures of the anterior sidewall 10 may useful to permitthe implant 1, and particularly first and second curved portions 10 a,10 b, to be substantially located between the cortical rims of thesupported vertebrae without extending beyond the bounds of the corticalrims. The cortical rim 610 provides more support than the interior,cancellous bone 620 of the vertebral body V.

Also contemplated is a method for inserting an intervertebral implant isprovided that includes means for accessing a collapsed spinal discspace. A number of trial bodies are provided with leading end portionssized for insertion into a non-distracted disc space. The trial bodiesare sequentially inserted into and removed from the disc space. Thetrial instrument providing the desired disc space height is used toselect an implant having a height and a self-distracting leading endportion corresponding to the height and leading end portion of the lastinserted trial instrument. The implant is then inserted into thenon-distracted disc space to restore the disc space and post-operativelymaintain the desired disc space height.

While embodiment of the invention have been illustrated and described indetail in the disclosure, the disclosure is to be considered asillustrative and not restrictive in character, and that all changes andmodifications that come within the spirit of the invention are desiredto be protected.

1. An implant with an elongated body positionable in a spinal disc spacecomprising: a convexly curved upper surface orientable toward anendplate of an upper vertebra; a convexly curved lower surfaceorientable toward an endplate of a lower vertebra; a leading end portionand an opposite trailing end portion; an at least partially convexlycurved anterior sidewall extending between the leading end portion andthe trailing end portion; and a posterior sidewall extending between theleading end portion and the trailing end portion; wherein the bodyincludes a height between the upper and lower surfaces corresponding toa desired disc space height between the upper vertebra endplate and thelower vertebra endplate; and wherein the leading end portion isstructured for insertion into the disc space in an at least partiallycollapsed condition and the height is sized to restore the collapseddisc space to the desired disc space height as the body is inserted inthe collapsed disc space.
 2. The implant of claim 1 wherein the uppersurface and the lower surface are each convexly curved along an entirelength of the body.
 3. The implant of claim 1 wherein the leading endportion includes a nose rounded between the upper surface and the lowersurface.
 4. The implant of claim 3 wherein the nose is rounded betweenthe sidewalls.
 5. The implant of claim 1 wherein an average height ofthe anterior sidewall is greater than an average height of the posteriorsidewall.
 6. The implant of claim 1 wherein the trailing end portion isplanar and extends between the sidewalls and the upper and lowersurfaces.
 7. The implant of claim 1 wherein the body includes: a firstnotch in a first one of the sidewalls; and a second notch in a secondone of the pair of sidewalls.
 8. The implant of claim 7 furthercomprising a coupling member having first and second fingerspositionable in respective ones of the first and second notches tosecure the body to the coupling member.
 9. The implant of claim 1wherein the upper and lower surfaces each include a number of engagementmembers therealong and projecting outwardly therefrom to engage bonytissue of the adjacent vertebral endplate when the body is positioned inthe spinal disc space.
 10. The implant of claim 9 wherein the engagementmembers comprise a number of teeth along portions of the sidewalls. 11.The implant of claim 10 wherein the teeth are raked toward the directionof implant insertion.
 12. An implant with an elongated body positionablein a spinal disc space comprising: an upper surface orientable toward anendplate of an upper vertebra; a lower surface orientable toward anendplate of a lower vertebra; a leading end portion and an oppositetrailing end portion; an at least partially convexly curved anteriorsidewall extending between the leading end portion and the trailing endportion; and a posterior sidewall extending between the leading endportion and the trailing end portion, the posterior sidewall having anaverage height less than the average height of the anterior sidewall;and wherein at least one of the upper surface and the lower surface arecurved such that a height of the implant near its center is greater thana height of the implant at its leading end; and wherein the height ofthe implant near its center is between about 7 mm and 19 mm; and whereinthe height of the implant at its leading end is at least about 3 mm lessthan the height of the implant near its center.
 13. The implant of claim12 wherein the upper surface and the lower surface are each convexlycurved along an entire length of the body.
 14. The implant of claim 12wherein the leading end portion includes a nose rounded between theupper surface and the lower surface.
 15. The implant of claim 14 whereinthe nose is rounded between the sidewalls.
 16. The implant of claim 12wherein the trailing end portion is planar and extends between thesidewalls and the upper and lower surfaces.
 17. The implant of claim 12wherein the body includes: a first notch in a first one of thesidewalls; and a second notch in a second one of the pair of sidewalls.18. The implant of claim 17 further comprising a coupling member havingfirst and second fingers positionable in respective ones of the firstand second notches to secure the body to the coupling member.
 19. Theimplant of claim 12 wherein the upper and lower surfaces each include anumber of engagement members therealong and projecting outwardlytherefrom to engage bony tissue of the adjacent vertebral endplate whenthe body is positioned in the spinal disc space.
 20. The implant ofclaim 19 wherein the engagement members comprise a number of teeth alongportions of the sidewalls.
 21. The implant of claim 20 wherein the teethare raked toward the direction of implant insertion.
 22. The implant ofclaim 12 wherein the height of the implant near its center is betweenabout 13 mm and 19 mm, and the height of the implant at its leading endis between about 4 mm and 9 mm.
 23. The implant of claim 12 wherein theheight of the implant near its center is between about 9 mm and 13 mm,and the height of the implant at its leading end is between about 4 mmand 7 mm.
 24. The implant of claim 12 wherein the height of the implantnear its center is between about 6 mm and 9 mm, and the height of theimplant at its leading end is between about 3 mm and 5 mm.
 25. Animplant with an elongated body positionable in a spinal disc spacecomprising: a convexly curved upper surface; a convexly curved lowersurface; a leading end portion defined by a convexly curved surface thatextends between the upper surface and the lower surface; a trailing endportion defined by a substantially planar surface that extends betweenthe upper surface and the lower surface; an anterior sidewall defined bya maximally anterior portion, a first curved portion extending betweenthe leading end portion and the maximally anterior portion, and a secondcurved portion extending between the trailing end portion and themaximally anterior portion; and a posterior sidewall extending betweenthe leading end portion and the trailing end portion; and wherein aheight of the implant near its center is between about 8 mm and 14 mm;and wherein a height of the implant at its leading end is at least about3 mm less than the height of the implant near its center.
 26. An implantwith an elongated body positionable in a spinal disc space comprising:an upper surface means orientable toward an endplate of an uppervertebra for substantially cooperatively fitting with the uppervertebra; a lower surface means orientable toward an endplate of a lowervertebra for substantially cooperatively fitting with the lowervertebra; a leading end means for promoting insertion of the implantbetween the upper vertebra and the lower vertebra, and an oppositetrailing end portion; an at least partially convexly curved anteriorsidewall means for enabling anterior placement of a portion of theimplant between the cortical rim of the upper vertebra and the corticalrim of the lower vertebra; and a posterior sidewall extending betweenthe leading end means and the trailing end portion; and wherein a heightof the implant near its center is between about 7 mm and 19 mm; andwherein a height of the implant at its leading end is at least about 3mm less than the height of the implant near its center.